Until recently, synthetic textile (ST) dust was thought to produce little or no adverse respiratory effects. This is in part because the composition of the dust was considered harmless and because the fibers were thought to be too large to deposit in the lower respiratory systems of exposed workers. For these reasons, ST dust is regulated under the classification, Particulate Not Otherwise Regulated (PNOR). Recent studies have found acute and chronic respiratory effects associated with ST dust at exposure levels well under the PNOR Permissible Exposure Limit (PEL). There is now also evidence that some fraction of ST dust can be deposited in all regions of the lung. To conduct future studies of the respiratory effects of ST dust, improved methods for assessing exposure are needed because the standard PNOR method does not assess the ST dust composition or the ST particle size fractions likely to deposit in specific regions of the lung. Part one of the proposed study will investigate several alternative methods for ST dust sampling and analysis and compare them to the standard PNOR method. Fifty-four matched sets (258 air filters) of air samples have already been collected using standard and alternative air monitoring methods in a side-by-side sampling scheme in a finishing department at a large ST mill. Using these air samples, three different quantitative exposure measures will be calculated: mass concentration, particle number concentration, and fiber number concentration. The composition of the ST dust that deposits in the three regions of the lung will also be determined. Qualitative ST dust exposure measures will be developed based on perceptions of dustiness recorded during the air monitoring. For each quantitative and qualitative exposure measure, the standard and alternative methods will be compared. The results will be used to recommend improved sampling and analytical methods for conducting an exposure assessment for ST dust in future occupational epidemiologic studies investigating respiratory disease. Part two of the proposed study will investigate ST dust exposure in the same local textile mill. Statistical modeling will be preformed to identify the production process determinants of the ST dust exposure measures. These results will be used to assist the mill in targeting specific aspects of the ST finishing process for ST dust control.